1. Field of the Invention
The present invention relates to: an apparatus and method for measuring the concentricity of two holes formed at ends of a cylinder; an apparatus and method for measuring the squareness of at least one end surface of a partition wall between two holes formed at ends of a cylinder to the longitudinal center line of at least one hole; and an apparatus and method for measuring the concentricity of two holes formed at ends of a cylinder and the squareness of at least one end surface of a partition wall between the two holes to the longitudinal center line of at least one hole.
2. Description of the Related Art
A cylinder provided with two holes at ends is used as a barrel member to hold one or more optical members including an objective lens and a solid-state image pickup device, at the distal end of an insertion portion of an endoscope, for example.
FIGS. 13A and 13B show a perspective view and a sectional view of a barrel member 10 of an endoscope. The barrel member 10 is made of stainless steel, and provided with two holes 11 and 12 at end surfaces 10a and 10b. A partition wall 13 is provided between the two holes 11 and 12 in the barrel member 10. A through hole 14 having a diameter smaller than that of each of the two holes 11 and 12 is formed in the partition wall 13.
The holes 11 and 12 and through hole 14 are arranged concentrically with a longitudinal center line LC of the barrel member 10.
The diameter of each of the two holes 11 and 12 is about 0.8 mm-about 1 mm. One hole 11 houses one or more optical members including a not-shown objective lens, and the other hole 12 houses a not-shown solid-state image pickup device.
For satisfactorily imaging a desired subject captured by one or more optical members including the objective lens by the solid-state image pickup device in the barrel member 10, it is necessary to exactly align the optical axes of the optical members with a line crossing at right angles to the center of the solid-state image pickup device (hereinafter called the optical axis). Further, in a case at least one end surface of the partition wall 13 is used as a reference for positioning one or more optical members and/or solid-state image pickup device in the direction along the longitudinal center line LC of the barrel member 10, it is necessary that at least one end surface of the partition wall 13 is precisely rectangular to the optical axes of one or more optical members and/or solid-state image pickup device.
This requires that the concentricity of the holes 11 and 12 to the longitudinal center line LC of the barrel member 10 is high, and the squareness of at least one end surface of the partition wall 13 to the longitudinal center line LC is high.
The concentricity of the holes 11 and 12 to the longitudinal center line LC of the barrel member 10 is measured by using a measuring microscope or a laser measuring instrument. Here, at first the center of the barrel member 10 in its radial direction is obtained by measuring the outer diameter of the barrel member 10 by using the measuring microscope or the laser measuring instrument. Then, the center of each of the holes 11 and 12 in their radial direction is obtained by measuring the inner diameter of each of the holes 11 and 12 of the barrel member 10 by using the measuring microscope or the laser measuring instrument. Finally, the displacement of the radial center of each of the holes 11 and 12 from the radial center of the barrel member 10, that is, the concentricity of the radial center of each of the holes 11 and 12 to the radial center of the barrel member 10, is obtained.
However, in the above described conventional method for measuring the concentricity by using the measuring microscope or the laser measuring instrument, it is impossible to simultaneously measure the concentricities of the radial centers of the two holes 11 and 12 to the radial center of the barrel member 10. Further, each of the measuring microscope and the laser measuring instrument can measure only the inner diameter of each of the holes 11 and 12 at their positions close to their inlets, and cannot measure the inner diameter of each hole at its position far from the inlet. Thus, in the above described conventional concentricity measuring method using the measuring microscope or the laser measuring instrument, it is impossible to measure the concentricity of the whole inner surface of each of the holes 11 and 12 along the longitudinal center line LC of the barrel member 10.
Other various types of concentricity measuring apparatuses are well known. For example, Jpn. Pat. Appln. KOKAI Publication No. 5-280957 discloses an apparatus for measuring the concentricity of an inner circumferential surface to an outer circumferential surface in a cylinder. Here, a cylinder placed on a V-block is rotated in its circumferential direction by a rubber roller pressed on the outer circumferential surface of the cylinder. Light is projected on one end of the cylinder while it is rotated, and the other end of the cylinder is shot by a TV camera. The concentricity of the inner circumferential surface to the outer circumferential surface in the cylinder is measured by measuring a displacement of the inlet edge of the hole of the cylinder at the other end in its radial direction.
The conventional concentricity measuring apparatus cannot measure the concentricity, unless the light projected on the one end of the rotating cylinder passes through the hole up to the other end. Further, since the outer circumferential surface of the cylinder placed on the V-block is used as a reference for the concentricity, the outer circumferential surface of the cylinder must be precisely.
For example, Jpn. Pat. Appln. KOKAI Publication No. 10-40749 discloses an apparatus for measuring the eccentricity (i.e. the concentricity) of an outer circumferential surface to a rotation center in a roller. Here, the rotation center of the roller is fixed to a rotation shaft, and the roller is rotated when the rotation shaft is rotated by a motor. A measuring probe of a dial gauge held by a holding means contacts the outer circumferential surface of the rotating roller, and the eccentricity of the outer circumferential surface of the rotating roller is measured by the dial gauge.
The above described conventional eccentricity measuring apparatus cannot measure the concentricity of the inner circumferential surface of the hole to the outer circumferential surface of the cylinder.
Various types of squareness measurement unit are also well known. For example, Jpn. Pat. Appln. KOKAI Publication No. 2001-108425 discloses an apparatus for measuring the squareness of an end surface of a columnar pin to a longitudinal center line of the pin. Here, a pointed end of a stopper is brought into contact with the rotation center of one end surface of the pin while it is rotated. Then, the one end surface is scanned from the rotation center to the outer edge in its radial direction by a laser beam from a laser displacement gauge, and the squareness of the one end surface is measured.
The above described conventional squareness measuring apparatus cannot measure the squareness of each end surface of a partition wall in a hole of a cylinder to the longitudinal center line of the cylinder.
Jpn. Pat. Appln. KOKAI Publication No. 11-295005 discloses specifically an apparatus for measuring the squareness of an actuator mounting surface of a valve box to the longitudinal center line of a valve shaft projecting out from the actuator mounting surface. Here, a bracket supporting a dial gauge is rotatably held on a part of the valve shaft projecting out from the actuator mounting surface. While the bracket rotates on the valve shaft, the height of the actuator mounting surface (that is, the squareness of the actuator mounting surface to the longitudinal center line of the valve shaft) is measured by the dial gauge held by the bracket.
The above described conventional squareness measuring apparatus cannot measure the squareness of an end surface of a partition wall in a hole of a cylinder to the longitudinal center line of the cylinder.